Mizuki Mochizuki is a high school student that one day meets a man by the name Adam. In the two weeks they are together, she falls in love with him, and the day he is to leave, she decides to follow him. Bringing her passport and a bag, she crosses one of Shibuya's many streets, on a red light, to follow after him. Only, when her ex-boyfriend calls out her name, she turns around, in the middle of the street, to see him running after her. While standing there, she is hit by a car.

Some time later, a girl named Hotaru, who has lost her cat, mistakes a stray as her own. The cat wanders into an abandoned home, and she squeezes through the bars to follow after the cat. When realizing that the cat isn't hers, she decides to leave, but is drawn in by a beautiful melody. She makes her way to where the sound is coming from, and discovers a girl playing a piano. After telling her friends about the girl, they all leave to check out the scene. When they go there, they cannot see the girl, but knows she is real when Hotaru hands her a notebook, and she takes it from Hotaru's hands. They have no idea who this girl is, but they are determined to find out just who she is and why she is there. The rest of the story follows their discoveries of the ghost they call Eve.